winVersion: recognize build 26300 as Windows 11 Version 26H2 (2026 update)

[josephsl]

Link to issue number:

Closes #20559

Summary of the issue:

On June 19, 2026, Microsoft announced Windows 11 Version 26H2 with the build number of 26300.

Description of user facing changes:

None

Description of developer facing changes:

source/winVersion.py:

• Updated copyright header
• Added constants for Windows 11 26H2 including build to release names mapping

Description of development approach:

Added winVersion.WIN11_26H2 as the constant representing Windows 11 Version 26H2. Testing (see below) requires computers running builds below, on, and above 26300. The computer used to develop this PR runs build 26300 (Insider Preview).

Testing strategy:

Manual:

Prerequisite: prepare three computers or virtual machines: a mahcine running a build below 26300 (25H2 (26200) will do), a computer subscribed to Windows Insider Experimental channel and WinVer shows build 26300, a machine running a build above 26300 (say, 26H1 stable build (28000)).

Procedure:

1. Open Python Console.
2. Import winVersion module, then define WIN11_26H2 as winVersion.WinVersion(major=10, minor=0, build=26300).
3. Check the just defined constant against winVersion.getWinVer() function output (specifically, winVersion.getWinVer() >= WIN11_26H2)..

Result:

• Below 26300: winVersion.getWinVer() >= WIN11_26H2 -> False
• Builds on or above 26300: winVersion.getWinVer() >= WIN11_26H2 -> True

Known issues with pull request:

None for most cases. Note that Windows 11 Version 26H1 has a higher build number than 26H2.

Code Review Checklist:

• Documentation:
  • Change log entry
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English
• API is compatible with existing add-ons.
• Security precautions taken.

[seanbudd]

has this version been released yet? As per previous PRs, we would rather not land code guessing at build versions until MS has fully committed to them by an actual release, not an announcement

[josephsl]

Hi,

Not yet. We will know when build 26300 lands in the release preview channel. Happy to push this to 2027.1 milestone.

Thanks.